SIDR G. Huston
Internet-Draft G. Michaelson
Intended status: Standards Track R. Loomans
Expires: March 19, 2010 APNIC
September 15, 2009
A Profile for X.509 PKIX Resource Certificatesdraft-ietf-sidr-res-certs-17
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Abstract
This document defines a standard profile for X.509 certificates for
the purposes of supporting validation of assertions of "right-of-use"
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Internet-Draft Resource Certificate Profile September 20091. Introduction
This document defines a standard profile for X.509 certificates
[X.509] for use in the context of certification of IP Addresses and
AS Numbers. Such certificates are termed here "Resource
Certificates." Resource Certificates are X.509 certificates that
conform to the PKIX profile [RFC5280], and also conform to the
constraints specified in this profile. Resource Certificates attest
that the issuer has granted the subject a "right-of-use" for a listed
set of IP addresses and Autonomous System numbers.
A Resource Certificate describes an action by a certificate issuer
that binds a list of IP Address blocks and AS Numbers to the subject
of the issued certificate. The binding is identified by the
association of the subject's private key with the subject's public
key contained in the Resource Certificate, as signed by the private
key of the certificate's issuer.
In the context of the public Internet, and the use of public number
resources within this context, it is intended that Resource
Certificates are used in a manner that is explicitly aligned to the
public number resource distribution function. Specifically, when a
number resource is allocated or assigned by a number registry to an
entity, this allocation is described by an associated Resource
Certificate. This certificate is issued by the number registry, and
the subject public key that is certified by the issuer corresponds to
the public part of a key pair for which the private key is associated
with the entity who is the recipient of the number assignment or
allocation. A critical extension to the certificate enumerates the
IP Resources that were allocated or assigned by the issuer to the
entity. In the context of the public number distribution function,
this corresponds to a hierarchical PKI structure, where Resource
Certificates are issued in only one 'direction' and there is a unique
path of certificates from a certification authority operating at the
apex of a resource distribution hierarchy to a valid certificate.
Validation of a Resource Certificate in such a hierarchical PKI can
be undertaken by establishing a valid issuer-subject certificate
chain from a certificate issued by a trust anchor certification
authority to the certificate [RFC4158], with the additional
constraint of ensuring that each subject's listed resources are fully
encompassed by those of the issuer at each step in the issuer-subject
certificate chain. Validation therefore logically corresponds to
validation of an associated set of assignment or allocation actions
of IP number resources.
Resource Certificates may be used in the context of the operation of
secure inter-domain routing protocols to convey a right-of-use of an
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Internet-Draft Resource Certificate Profile September 2009
IP number resource that is being passed within the routing protocol,
allowing relying parties to verify legitimacy and correctness of
routing information. Related use contexts include validation of
Internet Routing Registry objects, validation of routing requests,
and detection of potential unauthorized use of IP addresses.
This profile defines those fields that are used in a Resource
Certificate that MUST be present for the certificate to be valid.
Relying Parties SHOULD check that a Resource Certificate conforms to
this profile as a requisite for validation of a Resource Certificate.
1.1. Terminology
It is assumed that the reader is familiar with the terms and concepts
described in "Internet X.509 Public Key Infrastructure Certificate
and Certificate Revocation List (CRL) Profile" [RFC5280], "X.509
Extensions for IP Addresses and AS Identifiers" [RFC3779], "Internet
Protocol" [RFC0791], "Internet Protocol Version 6 (IPv6) Addressing
Architecture" [RFC4291], "Internet Registry IP Allocation Guidelines"
[RFC2050], and related regional Internet registry address management
policy documents.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119.
2. Describing Resources in Certificates
The framework for describing an association between the subject of a
certificate and the resources currently under the subject's control
is described in [RFC3779].
There are three aspects of this resource extension that are noted in
this profile:
1. RFC 3779 notes that a resource extension SHOULD be a CRITICAL
extension to the X.509 Certificate. This Resource Certificate
profile further specifies that the use of this certificate
extension MUST be used in all Resource Certificates and MUST
be marked as CRITICAL.
2. RFC 3779 defines a sorted canonical form of describing a
resource set, with maximal spanning ranges and maximal
spanning prefix masks as appropriate. All valid certificates
in this profile MUST use this sorted canonical form of
resource description in the resource extension field.
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Internet-Draft Resource Certificate Profile September 2009
3. A test of the resource extension in the context of certificate
validity includes the condition that the resources described
in the immediate parent CA certificate in the PKI (the
certificate where this certificate's issuer is the subject)
has a resource set (called here the "issuer's resource set")
that MUST encompass the resource set of the issued
certificate. In this context "encompass" allows for the
issuer's resource set to be the same as, or a strict superset
of, any subject's resource set.
Certificate validation entails the construction of a sequence of
valid certificates in an issuer-subject chain (where the subject
field of one certificate appears as the issuer in the next
certificate in the sequence) from a trust anchor to the certificate
being validated. Moreover, the resource extensions in this
certificate sequence from the first CA under the trust anchor to the
certificate being validated form a sequence of encompassing
relationships in terms of the resources described in the resource
extension.
3. Resource Certificate Fields
A Resource Certificate is a valid X.509 v3 public key certificate,
consistent with the PKIX profile [RFC5280], containing the fields
listed in this section. Unless specifically noted as being OPTIONAL,
all the fields listed here MUST be present, and any other field MUST
NOT appear in a conforming Resource Certificate. Where a field value
is specified here this value MUST be used in conforming Resource
Certificates.
3.1. Version
Resource Certificates are X.509 Version 3 certificates. This field
MUST be present, and the Version MUST be 3 (i.e. the value of this
field is 2).
3.2. Serial number
The serial number value is a positive integer that is unique per
Issuer.
3.3. Signature Algorithm
This field describes the algorithm used to compute the signature on
this certificate. The algorithm used in this profile is specified in
[ID.sidr-rpki-algs].
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Internet-Draft Resource Certificate Profile September 20093.4. Issuer
This field identifies the entity that has signed and issued the
certificate. The value of this field is a valid X.501 distinguished
name. Conventions are imposed on Issuer names used in resource
certificates, as described in [ID.sidr-arch].
If the certificate is a subordinate certificate issued by virtue of
the "cA" bit set in the immediate superior certificate, then the
issuer name MUST correspond to the subject name as contained in the
immediate superior certificate.
3.5. Subject
This field identifies the entity to whom the resource has been
allocated / assigned. The value of this field is a valid X.501
distinguished name. As noted above, conventions are imposed on
Subject names used in resource certificates, as described in
[ID.sidr-arch].
In this profile the subject name is determined by the issuer, and
each distinct subordinate CA and EE certified by the issuer MUST be
identified using a subject name that is unique per issuer.
In this context "distinct" is defined as an entity and a given public
key. An issuer SHOULD use a different subject name if the subject
entity or the subject entity's key pair has changed.
3.6. Valid From
The starting time at which point the certificate is valid. In this
profile the "Valid From" time SHOULD be no earlier than the time of
certificate generation. As per Section 4.1.2.5 of [RFC5280],
Certification Authorities (CAs) conforming to this profile MUST
always encode the certificate's "Valid From" date through the year
2049 as UTCTime, and dates in 2050 or later MUST be encoded as
GeneralizedTime. These two time formats are defined in [RFC5280].
In this profile, it is valid for a certificate to have a value for
this field that pre-dates the same field value in any superior
certificate. Relying Parties should not attempt to infer from this
time information a certificate was valid at a time in the past, or
will be valid at a time in the future, as the scope of a relying
party's test of validity of a certificate refers specifically to
validity at the current time.
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Internet-Draft Resource Certificate Profile September 20093.7. Valid To
The Valid To time is the date and time at which point in time the
certificate's validity ends. It represents the anticipated lifetime
of the resource allocation / assignment arrangement between the
issuer and the subject. As per Section 4.1.2.5 of [RFC5280], CAs
conforming to this profile MUST always encode the certificate's
"Valid To" date through the year 2049 as UTCTime, and dates in 2050
or later MUST be encoded as GeneralizedTime. These two time formats
are defined in [RFC5280].
As noted above, it is valid for a certificate to have a value for
this field that post-dates the same field value in any superior
certificate. The same caveats apply to Relying Party's assumptions
relating to the certificate's validity at any time other than the
current time,
While a CA is typically advised against issuing a certificate with a
validity interval that exceeds the validity interval of the CA's
certificate that will be used to validate the issued certificate, in
the context of this profile, it is anticipated that a CA may have
valid grounds to issue a certificate with a validity interval that
exceeds the validity interval of its certificate.
3.8. Subject Public Key Info
This field specifies the subject's public key and the algorithm with
which the key is used. The algorithm used in this profile is
specified in [ID.sidr-rpki-algs].
It is noted that larger key sizes are computationally expensive for
both the CA and relying parties, indicating that care should be taken
when deciding to use larger than the minimum key size noted in
[ID.sidr-rpki-algs]..
3.9. Resource Certificate Version 3 Extension Fields
As noted in Section 4.2 of [RFC5280], each extension in a certificate
is designated as either critical or non-critical. A certificate-
using system MUST reject the certificate if it encounters a critical
extension it does not recognize; however, a non-critical extension
MAY be ignored if it is not recognized [RFC5280].
The following X.509 V3 extensions MUST be present in a conforming
Resource Certificate, except where explicitly noted otherwise.
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Internet-Draft Resource Certificate Profile September 20093.9.1. Basic Constraints
The basic constraints extension identifies whether the subject of the
certificate is a CA and the maximum depth of valid certification
paths that include this certificate.
The issuer determines whether the "cA" boolean is set. If this bit
is set, then it indicates that the subject is allowed to issue
resources certificates within this overall framework (i.e. the
subject is a CA).
The Path Length Constraint is not specified in this profile and MUST
NOT be present.
The Basic Constraints extension field is a critical extension in the
Resource Certificate profile, and MUST be present when the subject is
a CA, and MUST NOT be present otherwise.
3.9.2. Subject Key Identifier
The subject key identifier extension provides a means of identifying
certificates that contain a particular public key. To facilitate
certification path construction, this extension MUST appear in all
Resource Certificates. This extension is non-critical.
The value of the subject key identifier MUST be the value placed in
the key identifier field of the Authority Key Identifier extension of
all certificates issued by this subject.
The Key Identifier used here is the 160-bit SHA-1 hash of the value
of the DER-encoded ASN.1 bit string of the subject public key, as
described in Section 4.2.1.2 of [RFC5280].
3.9.3. Authority Key Identifier
The authority key identifier extension provides a means of
identifying certificates that are signed by the issuer's private key,
by providing a hash value of the issuer's public key. To facilitate
path construction, this extension MUST appear in all Resource
Certificates. The keyIdentifier MUST be present in all Resource
Certificates, with the exception of a CA who issues a "self-signed"
certificate. The authorityCertIssuer and authorityCertSerialNumber
fields MUST NOT be present. This extension is non-critical.
The Key Identifier used here is the 160-bit SHA-1 hash of the value
of the DER-encoded ASN.1 bit string of the issuer's public key, as
described in Section 4.2.1.1 of [RFC5280].
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Internet-Draft Resource Certificate Profile September 20093.9.4. Key Usage
This describes the purpose of the certificate. This is a critical
extension, and it MUST be present.
In certificates issued to Certification Authorities only the
keyCertSign and CRLSign bits are set to TRUE and these MUST be the
only bits set to TRUE.
In end-entity certificates the digitalSignature bit MUST be set to
TRUE and MUST be the only bit set to TRUE.
3.9.5. Extended Key Usage
The Extended Key Usage Extension indicates one or more purposes for
which the public key in a certificate may be used. The uses are
specified via a SEQUENCE of one or more object identifiers (OIDs).
The EKU extension MUST NOT appear in any Certification Authority
certificate in the RPKI. This extension also MUST NOT appear in end
entity certificates used to verify RPKI objects such as ROAs or
manifests.
The EKU extension MAY appear in end entity certificates issued to
routers or other devices. The extension MUST NOT be marked critical.
Permitted values for the EKU OIDs will be specified in Standards
Track RFCs issued by other IETF working groups that adopt the RPKI
profile and that identify application-specific requirements that
motivate the use of such EKUs.
3.9.6. CRL Distribution Points
This field (CRLDP) identifies the location(s) of the CRL(s)
associated with certificates issued by this Issuer. This profile
uses the URI form of object identification. The preferred URI access
mechanism is a single RSYNC URI ("rsync://") [rsync] that references
a single inclusive CRL for each issuer.
In this profile the certificate issuer is also the CRL issuer,
implying at the CRLIssuer field MUST be omitted, and the
distributionPoint field MUST be present. The Reasons field MUST be
omitted.
The distributionPoint MUST contain GeneralNames, and MUST NOT contain
a nameRelativeToCRLIssuer. The form of the generalName MUST be of
type URI.
In this profile, the scope of the CRL is specified to be all
certificates issued by this CA issuer.
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The sequence of distributionPoint values MUST contain only a single
DistributionPointName set. The DistributionPointName set MAY contain
more than one URI value. An RSYNC URI MUST be present in the
DistributionPointName set, and reference the most recent instance of
this issuer's certificate revocation list. Other access form URIs
MAY be used in addition to the RSYNC URI.
This extension MUST be present and it is non-critical. There is one
exception, namely where a CA distributes its public key in the form
of a "self-signed" certificate, the CRLDP MUST be omitted.
3.9.7. Authority Information Access
This extension (AIA) identifies the point of publication of the
certificate that is issued by the issuer's immediate superior CA,
where this certificate's issuer is the subject. In this profile a
single reference object to publication location of the immediate
superior certificate MUST be used, except in the case where a CA
distributes its public key in the form of a "self-signed"
certificate, in which case the AIA field SHOULD be omitted.
This profile uses a URI form of object identification. The preferred
URI access mechanisms is "rsync", and an RSYNC URI MUST be specified
with an accessMethod value of id-ad-caIssuers. The URI MUST
reference the point of publication of the certificate where this
issuer is the subject (the issuer's immediate superior certificate).
Other accessMethod URIs referencing the same object MAY also be
included in the value sequence of this extension.
When an Issuer re-issues a CA certificate, the subordinate
certificates need to reference this new certificate via the AIA
field. In order to avoid the situation where a certificate re-
issuance necessarily implies a requirement to re-issue all
subordinate certificates, CA Certificate issuers SHOULD use a
persistent URL name scheme for issued certificates. This implies
that re-issued certificates overwrite previously issued certificates
to the same subject in the publication repository, and use the same
publication name as previously issued certificates. In this way
subordinate certificates can maintain a constant AIA field value and
need not be re-issued due solely to a re-issue of the superior
certificate. The issuers' policy with respect to the persistence of
name objects of issued certificates MUST be specified in the Issuer's
Certification Practice Statement.
This extension is non-critical.
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Internet-Draft Resource Certificate Profile September 20093.9.8. Subject Information Access
This extension (SIA) identifies the location of information and
services relating to the subject of the certificate in which the SIA
extension appears. Where the Subject is a CA in this profile, this
information and service collection will include all current valid
certificates that have been issued by this subject that are signed
with the subject's corresponding private key.
This profile uses a URI form of location identification. The
preferred URI access mechanism is "rsync", and an RSYNC URI MUST be
specified, with an accessMethod value of id-ad-caRepository when the
subject of the certificate is a CA. The RSYNC URI MUST reference an
object collection rather than an individual object and MUST use a
trailing '/' in the URI.
Other accessMethod URIs that reference the same location MAY also be
included in the value sequence of this extension. The ordering of
URIs in this sequence reflect the subject's relative preferences for
access methods to be used by parties for retrieval of objects from
the associated repository publication point, with the first method in
the accessMethod sequence being the most preferred.
This extension MUST be present when the subject is a CA, and is non-
critical.
For End Entity (EE) certificates, where the subject is not a CA, this
extension MAY be present, and is non-critical. If present, it either
references the location where objects signed by the private key
associated with the EE certificate can be accessed, or, in the case
of single-use EE certificates it references the location of the
single object that has been signed by the corresponding private key.
When the subject is an End Entity, and it publishes objects signed
with the matching private key in a repository, the directory where
these signed objects is published is referenced the id-ad-
signedObjectRepository OID.
id-ad OBJECT IDENTIFIER ::= { id-pkix 48 }
id-ad-signedObjectRepository OBJECT IDENTIFIER ::= { id-ad 9 }
When the subject is an End Entity, and it publishes a single object
signed with the matching private key, the location where this signed
object is published is referenced the id-ad-signedObject OID.
id-ad-signedObject OBJECT IDENTIFIER ::= { id-ad 11 }
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This profile requires the use of repository publication manifests
[ID.sidr-manifests] to list all signed objects that are deposited in
the repository publication point associated with a CA or an EE. The
publication point of the manifest for a CA or EE is placed in the SIA
extension of the CA or EE certificate. This profile uses a URI form
of manifest identification for the accessLocation. The preferred URI
access mechanisms is "rsync", and an RSYNC URI MUST be specified.
Other accessDescription fields may exist for the id-ad-rpkiManifest
accessMethod, where the accessLocation value indicates alternate URI
access mechanisms for the same manifest object.
id-ad-rpkiManifest OBJECT IDENTIFIER ::= { id-ad 10 }
CA certificates MUST include in the SIA an accessMethod OID of id-ad-
rpkiManifest, where the associated accessLocation refers to the
subject's published manifest object as an object URL.
When an EE certificate is intended for use in verifying multiple
objects, EE certificate MUST include in the SIA an accessMethod OID
of id-ad-rpkiManifest, where the associated accessLocation refers to
the EE's published manifest object as an object URL.
When an EE certificate is used to verify a single published object,
the EE certificate MUST include in the SIA an accessMethod OID of id-
ad-signedObject, where the associated accessLocation refers to the
publication point of the single object that is verified using this EE
certificate. In this case, the SIA MUST NOT include the accessMethod
OID of id-ad-rpkiManifest.
3.9.9. Certificate Policies
This extension MUST reference the Resource Certificate Policy, using
the OID Policy Identifier value of "1.3.6.1.5.5.7.14.2". This field
MUST be present and MUST contain only this value for Resource
Certificates.
No PolicyQualifiers are defined for use with this policy and thus
none must be included in this extension.
This extension MUST be present and it is critical.
3.9.10. IP Resources
This extension contains the list of IP address resources as per
[RFC3779]. The value may specify the "inherit" element for a
particular AFI value. In the context of resource certificates
describing public number resources for use in the public Internet,
the SAFI value MUST NOT be used. All Resource Certificates MUST
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include an IP Resources extension, an AS Resources extension, or both
extensions.
This extension, if present, MUST be marked critical.
Either the IP Resources extension, or the AS Resources extension, or
both, MUST be present in all RPKI certificates.
3.9.11. AS Resources
This extension contains the list of AS number resources as per
[RFC3779], or may specify the "inherit" element. RDI values are NOT
supported in this profile and MUST NOT be used. All Resource
Certificates MUST include an IP Resources extension, an AS Resources
extension, or both extensions.
This extension, if present, MUST be marked critical.
Either the IP Resources extension, or the AS Resources extension, or
both, MUST be present in all RPKI certificates.
4. Resource Certificate Revocation List Profile
Each CA MUST issue a version 2 Certificate Revocation List (CRL),
consistent with [RFC5280]. The CRL issuer is the CA, and no indirect
CRLs are supported in this profile.
An entry MUST NOT be removed from the CRL until it appears on one
regularly scheduled CRL issued beyond the revoked certificate's
validity period, as required in [RFC5280].
This profile does not allow issuance of Delta CRLs.
The scope of the CRL MUST be "all certificates issued by this CA".
The contents of the CRL are a list of all non-expired certificates
that have been revoked by the CA.
No CRL fields other than those listed here are permitted in CRLs
issued under this profile. Unless otherwise indicated, these fields
MUST be present in the CRL. Where two or more CRLs issued by a
single CA with the same scope, the CRL with the highest value of the
"CRL Number" field supersedes all other CRLs issued by this CA.
4.1. Version
Resource Certificate Revocation Lists are Version 2 certificates (the
integer value of this field is 1).
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Internet-Draft Resource Certificate Profile September 20094.2. Issuer Name
The value of this field is the X.501 name of the issuing CA who is
also the signer of the CRL, and is identical to the Issuer name in
the Resource Certificates that are issued by this issuer.
4.3. This Update
This field contains the date and time that this CRL was issued. The
value of this field MUST be encoded as UTCTime for dates through the
year 2049, and MUST be encoded as GeneralizedTime for dates in the
year 2050 or later.
4.4. Next Update
This is the date and time by which the next CRL SHOULD be issued.
The value of this field MUST be encoded as UTCTime for dates through
the year 2049, and MUST be encoded as GeneralizedTime for dates in
the year 2050 or later.
4.5. Signature
This field contains the algorithm used to sign this CRL. The
algorithm used in this profile is specified in [ID.sidr-rpki-algs].
It is noted that larger key sizes are computationally expensive for
both the CRL Issuer and relying parties, indicating that care should
be taken when deciding to use larger than the default key size
specified in [ID.sidr-rpki-algs].
4.6. Revoked Certificate List
When there are no revoked certificates, then the revoked certificate
list MUST be absent.
For each revoked resource certificate only the following fields MUST
be present. No CRL entry extensions are supported in this profile,
and CRL entry extensions MUST NOT be present in a CRL.
4.6.1. Serial Number
The serial number of the revoked certificate.
4.6.2. Revocation Date
The time the certificate was revoked. This time MUST NOT be a future
date (i.e., a date later than ThisUpdate). The value of this field
MUST be encoded as UTCTime for dates through the year 2049, and MUST
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be encoded as GeneralizedTime for dates in the year 2050 or later.
4.7. CRL Extensions
The X.509 v2 CRL format allows extensions to be placed in a CRL. The
following extensions are supported in this profile, and MUST be
present in a CRL.
4.7.1. Authority Key Identifier
The authority key identifier extension provides a means of
identifying the public key corresponding to the private key used to
sign a CRL. Conforming CRL issuers MUST use the key identifier
method. The syntax for this CRL extension is defined in section4.2.1.1 of [RFC5280].
This extension is non-critical.
4.7.2. CRL Number
The CRL Number extension conveys a monotonically increasing sequence
number of positive integers for a given CA and scope. This extension
allows users to easily determine when a particular CRL supersedes
another CRL. The highest CRL Number value supersedes all other CRLs
issued by the CA with the same scope.
This extension is non-critical.
5. Resource Certificate Request Profile
A resource certificate request MAY use either of PKCS#10 or
Certificate Request Message Format (CRMF). A CA Issuer MUST support
PKCS#10 and a CA Issuer may, with mutual consent of the subject,
support CRMF.
5.1. PCKS#10 Profile
This profile refines the specification in [RFC2986], as it relates to
Resource Certificates. A Certificate Request Message object,
formatted according to PKCS#10, is passed to a CA as the initial step
in issuing a certificate.
This request may be conveyed to the CA via a Registration Authority
(RA), acting under the direction of a Subject.
With the exception of the public key related fields, the CA is
permitted to alter any requested field when issuing a corresponding
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Internet-Draft Resource Certificate Profile September 2009
certificate.
5.1.1. PKCS#10 Resource Certificate Request Template Fields
This profile applies the following additional constraints to fields
that may appear in a CertificationRequestInfo:
Version
This field is mandatory and MUST have the value 0.
Subject
This field is optional. If present, the value of this field
SHOULD be empty, in which case the issuer MUST generate a
subject name that is unique in the context of certificates
issued by this issuer. If the value of this field is non-
empty, then the CA MAY consider the value of this field as the
subject's suggested subject name, but the CA is NOT bound to
honour this suggestion, as the subject name MUST be unique per
subordinate CA and EE in certificates issued by this issuer.
SubjectPublicKeyInfo
This field specifies the subject's public key and the algorithm
with which the key is used. The algorithm used in this profile
is specified in [ID.sidr-rpki-algs].
Attributes
[RFC2986] defines the attributes field as key-value pairs where
the key is an OID and the value's structure depends on the key.
The only attribute used in this profile is the ExtensionRequest
attribute as defined in [RFC2985]. This attribute contains
X509v3 Certificate Extensions. The profile for extensions in
certificate requests is specified in Section 5.3.
This profile applies the following additional constraints to fields
that MAY appear in a CertificationRequest Object:
signatureAlgorithm
The algorithm used in this profile is specified in
[ID.sidr-rpki-algs].
It is noted that larger key sizes are computationally expensive
for both the CA and relying parties, indicating that care
should be taken when deciding to use larger than the default
key size specified in [ID.sidr-rpki-algs].
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Internet-Draft Resource Certificate Profile September 20095.2. CRMF Profile
This profile refines the Certificate Request Message Format (CRMF)
specification in [RFC4211], as it relates to Resource Certificates.
A Certificate Request Message object, formatted according to the
CRMF, is passed to a CA as the initial step in issuing a certificate.
This request MAY be conveyed to the CA via a Registration Authority
(RA), acting under the direction of a subject.
With the exception of the public key related fields, the CA is
permitted to alter any requested field when issuing a corresponding
certificate.
5.2.1. CRMF Resource Certificate Request Template Fields
This profile applies the following additional constraints to fields
that may appear in a Certificate Request Template:
Version
This field MAY be absent, or MAY specify the request of a
Version 3 Certificate. It SHOULD be omitted.
SerialNumber
As per [RFC4211], this field is assigned by the CA and MUST be
omitted in this profile.
SigningAlgorithm
As per [RFC4211], this field is assigned by the CA and MUST be
omitted in this profile.
Issuer
This field is assigned by the CA and MUST be omitted in this
profile.
Validity
This field MAY be omitted. If omitted, the CA will issue a
Certificate with Validity dates as determined by the CA. If
specified, then the CA MAY override the requested values with
dates as determined by the CA.
Subject
This field is optional. If present, the value of this field
SHOULD be empty, in which case the issuer MUST generate a
subject name that is unique in the context of certificates
issued by this issuer. If the value of this field is non-
empty, then the CA MAY consider the value of this field as the
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subject's suggested subject name, but the CA is NOT bound to
honour this suggestion, as the subject name MUST be unique per
issuer in certificates issued by this issuer.
PublicKey
This field MUST be present.
extensions
This attribute contains X509v3 Certificate Extensions. The
profile for extensions in certificate requests is specified in
Section 5.3.
5.2.2. Resource Certificate Request Control Fields
The following control fields are supported in this profile:
Authenticator Control
It is noted that the intended model of authentication of the
subject is a "long term" model, and the advice as offered in
[RFC4211] is that the Authenticator Control field be used.
5.3. Certificate Extension Attributes in Certificate Requests
The following extensions MAY appear in a PKCS#10 or CRMF Certificate
Request. Any other extensions MUST NOT appear in a Certificate
Request. This profile places the following additional constraints on
these extensions.:
BasicConstraints
If this is omitted then the CA will issue an end entity
certificate with the BasicConstraints extension not present in
the issued certificate.
The Path Length Constraint is not supported in this Resource
Certificate Profile, and this field MUST be omitted in this
profile.
The CA MAY honour the SubjectType CA bit set to on. If this
bit is set, then it indicates that the Subject is allowed to
issue resource certificates within this overall framework.
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The CA MUST honour the SubjectType CA bit set to off (End
Entity certificate request), in which case the corresponding
end entity certificate will not contain a BasicConstraints
extension.
SubjectKeyIdentifier
This field is assigned by the CA and MUST be omitted in this
profile.
AuthorityKeyIdentifier
This field is assigned by the CA and MUST be omitted in this
profile.
KeyUsage
The CA MAY honour KeyUsage extensions of keyCertSign and
cRLSign if present, as long as this is consistent with the
BasicConstraints SubjectType sub field, when specified.
ExtendedKeyUsage
The CA MAY honour ExtendedKeyUsage extensions of keyCertSign
and cRLSign if present, as long as this is consistent with the
BasicConstraints SubjectType sub field, when specified.
SubjectInformationAccess
This field MUST be present when the subject is a CA, and the
field value SHOULD be honoured by the CA. If the CA is not
able to honour the requested field value, then the CA MUST
reject the Certificate Request.
This field (SIA) identifies the location of information and
services relating to the subject of the certificate in which
the SIA extension appears.
Where the subject is a CA in this profile, this information and
service collection will include all current valid certificates
that have been issued by this subject that are signed with the
subject's corresponding private key.
This profile uses a URI form of location identification. An
RSYNC URI MUST be specified, with an accessMethod value of id-
ad-caRepository when the subject of the certificate is a CA.
The RSYNC URI MUST reference an object collection rather than
an individual object and MUST use a trailing '/' in the URI.
Other accessMethod URIs that reference the same location MAY
also be included in the value sequence of this extension. The
ordering of URIs in this sequence reflect the subject's
relative preferences for access methods, with the first method
in the sequence being the most preferred by the Subject.
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A request for a CA certificate MUST include in the SIA of the
request the id-ad-caRepository accessMethod, and also MUST
include in the SIA of the request the accessMethod OID of id-
ad-rpkiManifest, where the associated accessLocation refers to
the subject's published manifest object as an object URL.
This field MAY be present when the subject is a EE. If it is
present the field value SHOULD be honoured by the CA. If the
CA is not able to honour the requested field value, then the CA
MUST reject the Certificate Request. If it is not present the
CA SHOULD honour this request and omit the SIA from the issued
certificate. If the CA is not able to honour the request to
omit the SIA, then the CA MUST reject the Certificate Request.
When an EE certificate is intended for use in verifying
multiple objects, the certificate request for the EE
certificate MUST include in the SIA of the request an
accessMethod OID of id-ad-signedObjectRepository, and also MUST
include in the SIA of the request an accessMethod OID of id-ad-
rpkiManifest, where the associated access location refers to
the publication point of the manifest object describing all
objects that are verified using this EE certificate.
When an EE certificate is used to sign a single published
object, the certificate request for the EE certificate MUST
include in the SIA of the request an accessMethod OID of id-ad-
signedObject, where the associated accessLocation refers to the
publication point of the single object that is verified using
this EE certificate, and MUST NOT include an id-ad-rpkiManifest
accessMethod OID in the SIA of the request.
In the case when the EE certificate is to be used exclusively
to sign one or more unpublished objects, such that the all
signed objects will not be published in any RPKI repository,
then the SIA SHOULD be omitted from the request.
CRLDistributionPoints
This field is assigned by the CA and MUST be omitted in this
profile.
AuthorityInformationAccess
This field is assigned by the CA and MUST be omitted in this
profile.
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CertificatePolicies
This field is assigned by the CA and MUST be omitted in this
profile.
With the exceptions of the publicKey field and the
SubjectInformationAccess field, the CA is permitted to alter any
requested field.
6. Resource Certificate Validation
This section describes the Resource Certificate validation procedure.
This refines the generic procedure described in section 6 of
[RFC5280].
To meet this goal, the path validation process verifies, among other
things, that a prospective certification path (a sequence of n
certificates) satisfies the following conditions:
1. for all 'x' in {1, ..., n-1}, the subject of certificate 'x'
is the issuer of certificate ('x' + 1);
2. certificate '1' is issued by a trust anchor ;
3. certificate 'n' is the certificate to be validated; and
4. for all 'x' in {1, ..., n}, certificate 'x' is valid.
6.1. Resource Extension Validation
The IP Resources and AS Resources extensions definitions [RFC3779]
defines critical extensions for Internet number resources. These are
ASN.1 encoded representations of the IPv4 and IPv6 address range
(either as a prefix/length, or start-end pair) and an AS number set.
Valid Resource Certificates MUST have a valid IP address and/or AS
number resource extension. In order to validate a Resource
Certificate the resource extension MUST also be validated. This
validation process relies on definitions of comparison of resource
sets:
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more specific
Given two IP address or AS number contiguous ranges, A and B, A
is "more specific" than B if range B includes all IP addresses
or AS numbers described by range A, and if range B is larger
than range A.
equal
Given two IP address or AS number contiguous ranges, A and B, A
is "equal" to B if range A describes precisely the same
collection of IP addresses or AS numbers as described by range
B. The definition of "inheritance" in [RFC3779] is equivalent
to this "equality" comparison.
encompass
Given two IP address and AS number sets X and Y, X
"encompasses" Y if, for every contiguous range of IP addresses
or AS numbers elements in set Y, the range element is either
more specific than or equal to a contiguous range element
within the set X.
Validation of a certificate's resource extension in the context of an
ordered certificate sequence of {1,2, ... , n} where certificate '1'
is issued by a trust anchor and certificate 'n' is the target
certificate, and where the subject of certificate 'x' is the issuer
of certificate ('x' + 1), includes verification that that the
resources described in certificate 'x' "encompass" the resources
described in certificate ('x' + 1), and the resources described in
the trust anchor information "encompass" the resources described in
certificate '1'.
6.2. Resource Certification Path Validation
Validation of signed resource data using a target resource
certificate consists of assembling an ordered sequence (or
'Certification Path') of certificates ({1,2,...n} where '1' is a
certificate that has been issued by a trust anchor, and 'n' is the
target certificate) verifying that all of the following conditions
hold:
1. The certificate can be verified using the Issuer's public key
and the signature algorithm
2. The current time lies within the certificate's Validity From
and To values.
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3. The certificate contains all fields that MUST be present and
contains field values as specified in this profile for all
field values that MUST be present.
4. No field value that MUST NOT be present in this profile is
present in the certificate.
5. The Issuer has not revoked the certificate by placing the
certificate's serial number on the Issuer's current
Certificate Revocation List, and the Certificate Revocation
List is itself valid.
6. That the resource extension data is "encompassed" by the
resource extension data contained in a valid certificate where
this Issuer is the Subject (the previous certificate in the
ordered sequence)
7. The Certification Path originates with a certificate issued by
a trust anchor, and there exists a signing chain across the
Certification Path where the Subject of Certificate 'x' in the
Certification Path matches the Issuer in Certificate ('x' + 1)
in the Certification Path.
A certificate validation algorithm may perform these tests in any
chosen order.
Certificates and CRLs used in this process may be found in a locally
maintained cache, maintained by a regular synchronization across the
distributed publication repository structure.
There exists the possibility of encountering certificate paths that
are arbitrarily long, or attempting to generate paths with loops as
means of creating a potential DOS attack on a relying party. Some
further heuristics may be required to halt the certification path
validation process in order to avoid some of the issues associated
with attempts to validate such structures. It is suggested that
implementations of Resource Certificate validation MAY halt with a
validation failure if the certification path length exceeds a locally
defined configuration parameter.
7. Design Notes
The following notes provide some additional commentary on the
considerations that lie behind some of the design choices that were
made in the design of this certificate profile. These notes do not
constitute a formal part of the profile specification, and the
interpretation of key words as defined in RFC2119 are not applicable
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in this section of the document.
Certificate Extensions:
This profile does not permit the use of any other critical or
non-critical extensions. The rationale for this restriction is
that the resource certificate profile is intended for a
specific use, and in this context it is not seen as being
appropriate to be in the position of having certificates with
additional non-critical extensions that relying parties may see
as valid certificates without understanding the extensions, but
were the relying party in a position to understand the
extensions, would contradict or qualify in some way this
original judgment of validity. This profile takes the position
of minimalism over extensibility. The specific goal for the
associated Resource Public Key Infrastructure to precisely
match the IP number resource allocation structure through an
aligned certificate structure that describes the allocation and
its context within the number resource distribution hierarchy.
The profile defines a resource certificate that is structured
to meet these requirements.
Certification Authorities and Key Values:
This profile uses a definition of an instance of a CA as a
combination of a named entity and a key pair. Within this
definition a CA instance cannot rollover a key pair. However,
the entity can generate a new instance of a CA with a new key
pair and roll over all the signed subordinate products to the
new CA.
This has a number of implications in terms of subject name
management, CRL Scope and repository publication point
management.
Subject Name:
For Subject Names the issuer should ensure that when an
entity requests a certificate with a new key pair, the CA
issues a certificate with a new subject name. One way to
achieve this is to use a CommonName value that is unique
per subordinate entity, using an algorithm of the CA's
devising to ensure this uniqueness, and for the CA to
include the serial number field of the X.501
distinguished name structure, with a serial number value
that is derived from the hash of the subject public key
value. It should also be noted that conventions are
imposed on Subject names used in resource certificates,
as described in [ID.sidr-arch], and that any name scheme
should comply with these conventions.
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CRL Scope:
For CRL Scope this profile specifies that a CA issues a
single CRL sequence, and the scope of the CRL is all
certificates issued by this CA. Because the CA instance
is bound to a single key pair this implies that the CA's
public key, the key used to validate the CA's CRL, and
the key used to validate the certificates revoked by that
CRL are all the same.
Repository Publication Point:
The definition of a CA affects the design of the
repository publication system. In order to minimize the
amount of forced re-certification on key rollover events,
a repository publication regime that uses the same
repository publication point for all CA instances that
refers to the same entity, but with different key values
will minimize the extent of re-generation of certificates
to only immediate subordinate certificates.
In order for two or more CA instances to share a single
repository publication point there needs to be a regime
of key management into OLD, CURRENT and FUTURE keys and a
similar regime of OLD, CURRENT and FUTURE CAs. An OLD CA
should regularly publish its CRL for as long as the OLD
CA instance is still valid, and issue EE certificates as
necessary to maintain a current manifest of all OLD CA
published products, but it should not sign any other
products. The CURRENT CA should publish its CRL, and
should publish all subordinate products, as well as
issuing EE certificates as necessary to maintain a
current manifest of all CURRENT CA published products.
FUTURE CAs should publish no products at all in the
repository publication point. It would be consistent
with this repository object name framework for the CRL
and manifest to be published using object names derived
from the hash of the public key value of the CA instance.
Key Rollover:
As a CA instance is associated with a single key pair, there
are some considerations regarding the procedure that should be
followed by an entity performing a key rollover function. The
entity will need to create a new CA instance and then use this
new CA instance to re-issue all subordinate products with the
new CA instance.
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To perform a key rollover operation the entity will need to:
1. Generate a NEW key pair.
2. Generate a certificate request with the NEW key
pair and pass the request to the entity's issuer.
3. Request the entity's issuer to generate and publish
a NEW CA certificate, with an issuer-selected
subject name that is distinct from the subject name
used in conjunction with the previous subject name
value for this entity.
4. Mark the CURRENT CA as OLD and the NEW CA as
CURRENT.
5. The CURRENT CA will generate new certificates for
all existing subordinate CA and EE certificates,
and publish those products in the same repository
publication point and with the same repository
publication point name as the previous OLD
subordinate CA and EE certificates. The keys in
these reissued certificates must not change.
6. Where the signing structure uses a packaging format
that includes the EE certificate within the signed
data, signed objects that included OLD EE
certificates in their signed data will need to be
re-signed using an EE certificate issued by the
CURRENT CA. In the case where the OLD EE
certificate is a "single use" EE certificate and
the associate private key has been destroyed this
will entail the generate of a new key pair, the
issuing of an EE certificate by the CURRENT CA. In
the case of a "multi-use" EE certificate, the EE
certificate should issued using the CURRENT CA.
The object, together with the issued EE
certificate, should be signed with the associated
private key, and published in the same repository
publication point, using the same repository
publication point name, as the previously signed
object that it replaces (i.e. overwrite the old
signed object).
7. Generate a certificate revocation request for the
OLD CA certificate and pass it to the entity's
issuer.
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8. Remove all published OLD CA products and destroy
the OLD private key.
Name Uniqueness:
This profile specifies that subject names must be unique per
issuer, and does not specify that subject names must be
globally unique.
Given that the Resource Certificate PKI is a distributed PKI,
there is no inherent ability for Certification authorities to
coordinate PKI-wide unique subject names. CA's should use
multi-attribute, structured Subject names in their RPKI
certificates. This advice is motivated by a desire to include
within this specification a CA's subject naming practice that
uses a distinguished name component that is constant for any
given entity that is the subject of CA-issued certificates (the
CommonName component of the Distinguished Name), yet still
ensure that the structures Subject name changes whenever
subject key rollover occurs (the serial number component of the
Distinguished Name). Also, as the publication repository is
distributed, and distinct entities use distinct repository
publication points any potential ambiguity is resolved by the
distinct publication point.
8. Security Considerations
The Security Considerations of [RFC5280] and [RFC3779]apply to
Resource Certificates as defined by this profile, and their use.
A Resource Certificate PKI cannot in and of itself resolve any forms
of ambiguity relating to uniqueness of assertions of rights of use in
the event that two or more valid certificates encompass the same
resource. If the issuance of resource certificates is aligned to the
status of resource allocations and assignments then the information
conveyed in a certificate is no better than the information in the
allocation and assignment databases.
9. IANA Considerations
[Note to IANA, to be removed prior to publication: there are no IANA
considerations stated in this document.]
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